[1]} explored how the Local Ensemble Transform Kalman filter could be used to assimilate in-situ observations of solar wind plasma properties into the ENLIL magnetohydrodynamic (MHD) solar wind model, which demonstrated clear improvements in the representivity of the ENLIL simulations. The Buger Radial Variational Data Assimilation (BRaVDA) scheme was developed in [2]}, in which a variational DA scheme was coupled to the hydrodynamic (HD) HUX solar wind model [3]}, for the assimilation of observations of the solar wind speed. Experiments with synthetic observations and solar wind speed observations from the STEREO spacecraft showed that BRaVDA reduced the errors in the solar wind speed predictions at Earth. This work was extended by [4]} to the HUXt model, a HD solar wind model with explicit time-dependence [5]}, [6]}, in which it was shown that over the period 2007-2014, BRaVDA returned a \(31\%\)  reduction in the RMSE of hindcasts of the solar wind speed at Earth.
